Camera-based driver assistance systems that detect the course of one's own roadway lane (called the ego-lane herein) on the basis of road markings, such as Lane Departure Warning (LDW) systems, have established themselves on the market in the meantime. In particular areas of application, the use of such systems is already mandatory.
Moreover, assistance systems for lane keeping support can intervene in vehicle steering. For example, EP 1414692 B1 shows a method for operating a driver assistance system of a vehicle with servo-assisted steering. A CCD camera covers, i.e. monitors or detects, the surroundings of the vehicle and estimates particularly the course of the traffic lane therefrom. The surroundings data are compared with motion data of the vehicle. On the basis of said comparison, support of the driver's steering operation can be initiated.
Typically, modern driver assistance systems detect the course of the markings of the ego-lane and of the adjacent traffic lanes and estimate therefrom the position of one's own vehicle or subject vehicle (called the ego-vehicle herein) relative to the lane markings.
DE 10 2005 033 641 A1 describes a display device with traffic lane detection presenting lane markings of the detected traffic lane on a display in such a manner that a quality of traffic lane detection is visible. It is possible to define, e.g., a brightness contrast or color contrast for grading the quality of traffic lane detection (detection is good, poor and impossible), said contrast being required for good detection or at least for poor detection. If the road marking is interrupted on a certain stretch of road and thus cannot be detected so that it is only possible to extrapolate the adjacent road markings for that gap, a lane marking representation differing from that of a consistently and reliably detected road marking is selected. It is also possible to include pavement boundary markings (e.g., delineator posts) in traffic lane detection.
In contrast to freeways and developed national highways, there are many roads that have no road markings or that are only partially provided with road markings. On many country roads, for example, only the middle of the pavement is marked as a separating line between the two traffic lanes. In most cases, there are no lateral boundaries and the drivers orientate themselves by delineator posts or by the surroundings or by the lateral boundary of the pavement. Modern driver assistance systems for lane detection notice the absence of markings and turn themselves off completely or switch over to appropriate modes in which only the existing markings are taken into consideration or take the quality of traffic lane detection into consideration when displaying the traffic lane as described above.
Future systems will have to be capable of detecting the ego-lane irrespective of the presence of markings since the demands on driver assistance systems are constantly increasing, especially with regard to autonomous safety functions, such as Emergency Brake Assist and Emergency Steer Assist.